1. Field of the Invention
The present invention relates to a polarizing plate protective film, a polarizing plate, and a display device.
2. Description of the Related Art
Liquid crystal display devices are gradually more widely used as space-saving type image display devices with low power consumption. Thinner liquid crystal display devices are even more required in accordance with an expansion of the market of so-called mobile devices such as mobile phones, tablet PCs, and the like, in addition to the market of televisions and the like in which high-definition images are required.
In a basic configuration of the liquid crystal display device, polarizing plates are provided on both sides of a liquid crystal cell. The polarizing plate has a role of passing light in a given direction, that is, only through the plane of polarization. In addition, performance of liquid crystal display devices greatly varies depending on the performance of polarizing plates. The polarizing plate is generally configured with a polarizer formed of a polyvinyl alcohol film and the like in which iodine or a dye is adsorbed and oriented, and transparent protective film (polarizing plate protective films) which are bonded to both front and rear sides of the polarizer.
When the polarizing plate is used for a long time, display performance is deteriorated due to heat, wet heat, or ultraviolet rays. The deterioration of the display performance is mainly due to deterioration of the polarizer configuring the polarizing plate. Along with the thinning of the polarizing plates, the polarizers are more easily deteriorated.
Meanwhile, means for adding an ultraviolet absorbent to a polarizing plate protective film are used to respond the deterioration of the display performance due to ultraviolet rays. However, regarding the deterioration of the polarizer due to heat or wet heat, although further improvement is required along with the thinning of the polarizing plates, there are presently no means for sufficiently dealing with such requirement.
In addition, a cross-linking agent disclosed in JP2008-7780A has been proposed as an additive to be added to the polarizing plate protective film. This is a technology of crosslinking a cellulose ester film to improve adhesiveness between the cellulose ester film and a polarizer and is not a technology of improving durability of a polarizing plate.